, and potentiometer. J have looked and so many diagrams and can't figure out how to wire this thing! I am a visual guy and need pictures. My fan has a red and white wire together going to a harness that has a red, yellow and 2 blacks. There is also a random yellow wire coming from the fan. Totally lost!!

I found some pictures on the webs that helped a lot and got it working just fine. My only issue is that when I tried a 12v plug it didn't work. I ended up using an old cell phone charger that's 5.7v or close to it. Definitely under 6v. The fan is not spinning nearly as fast as I want it to. Should I just use a plug/charger that has more voltage?

Got a new fan and it cranks!! Now I just have get my magnets in the proper spots... Should one be + side down and the other - side down? Any advantage to using 4??

No advantage that I can think of to using 4 magnets. I actually think it would cause you problems. Just make sure your magnets are oriented as you stated (one with + side up, other with - side up) and that the distance between your magnets, center-to-center, is about equal to the length of your stir bar. I positioned mine with double-sided tape until I got the position right, then glued them.

Having the magnets sit too close to the actual fan motor will significantly slow down the motor's rpm speeds. Folks will generally either used a piece of ferrous material to act as a kind of "magnetic shield" or will use some kind of spacer between the motor and magnets in order to get the magnets further away from the motor. I went with the latter option and ended up using an empty scotch tape spindle that gives about 3/4" spacing, but many folks use PVC fittings or pipe.

Magnets: Putting 4 magnets in a '+' formation would likely just cause problems, however doubling up the magnets across from each other will increase their magnetic pull and many people have actually had to do this to get the kind of magnetic strength they need. Yes, like scottsr123 said, make sure you have the magnets with opposite poles facing up across from each other. Most stirbars are magnetic with north on one end and south on the other so they'll need to attract to your fan-mounted magnets.